1. Field of the Invention
The present invention relates to an LED lighting module with a heat dissipation structure, and more particularly relates to a module having LEDs served as its light source and combined with a highly efficient heat dissipation structure.
2. Description of the Related Art
A light emitting diode (LED) is a highly efficient luminescent component for converting the electric energy into light energy, and also is a micro solid-state light source. The main portion of an LED device is a semiconductor p-n junction structure. After the two ends of the junction are applied with a voltage, the photon energy is emitted and the light ray of a specific wavelength range is emitted through the combination of electrons and holes. Since the LED device has the characteristics of color reproducibility and single wavelength, the LED has become a mainstream technology for improving the spectrum of the back light source for a liquid crystal display (LCD). Moreover, LED devices are also widely applied on an outdoor large display, and will gradually replace the current illumination devices.
When the back light source of an LCD utilizes LEDs as a light source, two common relative position relationships between the LEDs and the illumination surface are a direct type and an edge type. Usually, a large scale LCD adopts the direct type as an illuminating mode of the back light source. A heat dissipation structure of a common direct-type LED backlight module is to mount the LED devices on the surface of a printed circuit board (PCB) and then transfer the heat to heat sinks through heat pipes fixed on another opposite surface of the PCB for heat exchange.
FIG. 1 is a schematic diagram of a cross-sectional structure of a conventional backlight module. An earlier U.S. Patent Publication US 2006/0002142 has disclosed a backlight module 10, which includes LED devices 11, a PCB 12, heat pipes 13 and a bottom cover 14. The surface of the LED devices 11 is mounted on an upper surface of a metal core PCB 12, and the PCB 12 has a circuit layer for driving the LED devices 11 to illuminate. The heat is generated when the LED devices 11 are lighting on, and the heat accumulating in the LED devices 11 will cause their brightness decay. Therefore, the heat is taken away by the heat pipe 13 adhered to the back of the PCB 12, and transferred to a peripheral heat sink (not shown) through a heat path of the bottom cover 14, so as to be delivered to the atmosphere.
Moreover, an ROC Patent publication No. M284193 also discloses a backlight module 20, as show in FIG. 2. The backlight module 20 includes a plurality of LED devices 21 mounted on a PCB 22, and heat pipes 23 are adhered to a lower surface of the PCB 22. Heat sinks 24 are disposed at the periphery of the heat pipe 23, which deliver the heat taken away by the heat pipe from the PCB 22 to the atmosphere. A similar heat dissipation structure is also disclosed by the Japanese Patent Publication No. JP 2005317480.
However, the above conventional arts have the same heat dissipation paths, that is, the heat generated by the LED devices is transferred to the heat pipes via the PCB. However, either a cladding layer or an insulation layer of the PCB is made of the material of low heat conductivity, such as solder mask or resin, which causes a large thermal resistance of the PCB, thus the heat generated by the LED devices cannot be quickly and effectively transferred to the heat pipe. Even if the PCB is changed into a metal core PCB having lower thermal resistance, the heat generated by the LED still needs to pass through each lamination material of the metal core PCB and through the adhesive material or solder of the interface, and then reaches the heat pipe.
Therefore, an LED lighting module for shortening the heat conducting path and reducing the corresponding total thermal resistance is urgently needed in the LED application field, through which the heat generated by the LED devices may be directly and quickly transferred to the heat pipes, so as to improve the LED reliability and the luminous efficiency of the LED devices.